(1) Field of the Invention
This invention relates to a cut-in resistance for heating fans and, more particularly, a motor vehicle heating fan.
(2) Prior Art
In a known cut-in resistance for motor vehicle heating fans, the two windings made of resistance wire, which can be cut into the electric fan motor either alone or connected in series, are aligned lying one behind the other in the longitudinal direction on a plate made of insulating material. Their ends are clamped by bent parts of flat plug contacts penetrating the plate of insulating material. The two windings made of resistance wire are joined together by a soldered joint which is intended to melt and interrupt the current when the cut-in resistance overheats.
With this known construction of a cut-in resistance, many difficulties have arisen. When the cut-in resistance overheats due to a heavy-running electric fan motor or due to a cooling air supply interrupted by foreign bodies, although the safety solder joint becomes soft, it does not open due to deficient pretension at the two mutually connected ends of the windings. This results in a considerable overheating of the cut-in resistance over a long period whereby adjacent components made of plastics begin to melt or even in some cases to burn. These are some of the problems this invention overcomes.